The American Meteor Society has received reports of a bright fireball meteor being seen over northern Alabama slightly after 0.15 am local time on Wednesday 7 March 2018 (slightly after 5.15 am on Friday 17 August GMT). The event was witnessed from Kentucky, North Carolina, South Carolina and Georgia, though most of the reports came from Alabama. A fireball is defined as a meteor (shooting star) brighter than the planet Venus. These are typically caused by pieces of rock burning up in the atmosphere, but can be the result of man-made space-junk burning up on re-entry. The Object has been calculated to have been moving from southeast to northwest over the northern part of the state, and appears to have broken up about 30 km above the community of Grove Oak.
The 17 August 2018 fireball imaged from a meteor observing camera in the region. NASA Meteor Watch.
Objects of this size probably enter the Earth's atmosphere several times a year, though unless they do so over populated areas they are unlikely to be noticed. They are officially described as fireballs if they produce a light brighter than the planet Venus. The brightness of a meteor is caused by friction with the Earth's atmosphere, which is typically far greater than that caused by simple falling, due to the initial trajectory of the object. Such objects typically eventually explode in an airburst called by the friction, causing them to vanish as an luminous object. However this is not the end of the story as such explosions result in the production of a number of smaller objects, which fall to the ground under the influence of gravity (which does not cause the luminescence associated with friction-induced heating).
Map showing areas where sightings of the meteor were reported, and the route of the object (blue arrow). American Meteor Society.
These 'dark objects' do not continue along the path of the original bolide, but neither do they fall directly to the ground, but rather follow a course determined by the atmospheric currents (winds) through which the objects pass. Scientists are able to calculate potential trajectories for hypothetical dark objects derived from meteors using data from weather monitoring services.
Witness reports can help astronomers to understand these events. If you witness a fireball-type meteor over the UK you can report it to the American Meteor Society here.